Essentially he gets a redshirt semester and a chance to soak up the system.
Duke football has moved from a recruiting backwater to a desirable destination and may be increasing its appeal even more. Check out Mark Gilbert, for instance.
Gilbert, a Duke commit from Fayetteville, has given up a promising senior year of basketball to come to Duke early. He'll enroll in January.
Why? Well we're sure it's at least partly because he sees Duke as a great evironment and a place to learn more about his passion.
Presumably, if he wanted to and the circumstances were right, he could walk on to the basketball team at some point.